Archaeology & Evolution Glossary (N)

narrow-sense heritability: The proportion of the phenotypic variance that results from additive genetic variance.

nasal root: The top of the nose, the indentation at the suture where the nasal bones meet the frontal bone.

nasal spine (anterior): The thin projection of bone at the midline on the lower nasal margin, holding the cartilaginous center of the nose.

nasion: The point on the midline where the two nasal bones and the frontal come together.

nasoalveolar clivus: Portion of the premaxilla extending from the nasal cavity to the incisor root sockets.

nasofrontal suture: The suture along the upper border of the nasal bones with the frontal. Its shape can help determine geograohic origin.

nasolacrimal duct: See lacrimal duct.

nasospinale: Midpoint of the lower nasal aperture.

natural selection: Difference in reproductive success and/or survivorship of individuals that result in the unequal contribution of genotypes to the gene pool of the next generation.

neck: A constricted portion of a bone immediately below the “head”.

negative assortative mating: A mating that occurs between dissimilar individuals more often than it does between randomly chosen individuals.

negative feedback: In systems thinking, this is a process which acts to counter or “dampen” the potentially disruptive effects of external inputs; it acts as a stabilizing mechanism.

neocortex: The cortex, or outer surface of the cerebral hemispheres of the brain.

Neogene: A part of the Cenozoic including the Miocene and Pliocene.

Neolithic: An Old World chronological period characterized by the development of agriculture and, hence, an increasing emphasis on sedentism.

Neolithic Revolution: A term coined by V.G. Childe in 1941 to describe the origin and consequences of farming (i.e. the development of stock raising and agriculture), allowing the widespread development of settled village life.

neolocal: Residence of a couple after marriage in a new household not linked spatially to that of the groom’s or the bride’s kin (cf. virilocal, uxorilocal).

neonate: A newborn infacnt.

neural: Pertaining to a nerve or the nervous system.

neural canal: The large opening though the vertebrae than encloses the spinal cord, also called the vertebral canal.

neurocranium: The portion of the skull enclosing the brain, as distinct from the facial bones and the basicranium.

neuron: Nerve cell.

neutral evolution: Genetic changes that do not affect the fitness of the individual or its offspring.

neutral mutation: A base-pair change in the gene that changes a codon in the mRNA so that there is no change in the function of the protein translated from that message.

neutral-mutation hypothesis: A hypothesis that replaced the classical model by acknoledging the presence of extensive genetic variation in proteins, but proposing that this variation is neutral with regard to natural selection.

neutron activation analysis (NAA): A method used in the analaysis of artifact composition which depends on the excitation of the nuclei of the atoms of a sample’s various elements, when these are bombarded with slow neutrons. The method is accurate to about plus or minus 5 percent.

New Archaeology: A new approach advocated in the 1960s which argued for an explicitly scientific framework of archaeological method and theory, with hypotheses rigorously tested, as the proper basis for explanation rather than simply description.

New World primate: A primate from North or South America.

niche: The limited portions of the environment, in terms of space, resources, etc., that a species fits and/or that it requires for its survival and reproductive success.

NISP (number of identified specimens): A gross counting technique used in the quantification of animal bones. The method may rpoduce misleading results in assessing the relative abundance of different species, since skeletal differences and differential rates of bone preservation mean that some species will be represented more than others.

nitrogenous base: A nitrogen-containing base that, along with a pentose sugar and a phosphate, is one of the three parts of a nucleotide, the building block of RNA and DNA.

nocturnal: Primarily active during the night.

noncontributing alleles: The alleles that do not have any effect on the phenotype of the quantitative trait.

nondisjunction (primary disjunction): A failure of homologous chromosomes or sister chromatids to separate at anaphase.

nonhistone: A type of acidic or neutral protein found in a chromatin.

nonhomologous chromosomes: The chromosome containing dissimilar genes that do not pair during meiosis.

non-Mendelian inheritance (cytoplasmic inheritance): The inheritance of characters determined by genes not located on the nuclear chromosomes but on mitochondrial or chloroplast chromosomes. Such genes show inheritance patterns distinctively different from those of nuclear genes.

nonmetric trait: Feature whose expression is better or more accurately described as discrete charater states than as measurements.

nonparental-ditype (NPD): One of three types of tetrads possible when two genes are segregating in a cross. The NPD tetrad contains four nuclei, all of which have recombinant (non-parental) genotypes, that is, two of each possible type.

non-probabilistic sampling: A statistical sampling strategy which concentrates on sampling areas on the basis of intuition, historical documentation, or long field experience in the area.

nonsense codon: See chain-terminating codon.

nonsense mutation: A gene mutation in which a base-pair change in the DNA causes a change in an mRNA codon from an amino acid-coding codon to a chain-terminating (nonsense) codon. As a result, polypeptide chain synthesis is terminated prematurely and is therefore either nonfunctional or, at best, partially functional.

nontranscribed spacer (NTS) sequence: Sequences, which are not transcribed, found between transcription units in rDNA. Important sequences that control transcription of the rDNA are within the NTS.

non-unilineal descent: An alternative term to cognatic descent. Since cognatic descendants include patrilineal descendants and matrilineal descendants this usage is flawed. It has been suggested that the term be used in societies that recognize a unilineal core within a cognatic descent category to denot descent status through at least one alternate sex link (i.e., non-agnatic where descent includes at least one female link, nonuterine where it includes at least one male link).

normal distribution: A probability distribution in statistics, graphically displayed as a bell-shaped curve.

normal polarity epoch: Period of geological time in which the earth’s magnetic field is directed as it is at present.

norm of reaction: The extent to which the phenotype produced by a genotype varies with the environment.

northern blot analysis: A similar technique to Southern blotting except that RNA rather than DNA is separated and transferred to a filter for hybridization with a probe.

nuchal: Pertaining to the nape of the neck.

nuchal crest: A raised bony ridge on the back of the skull caused by the attachment of neck muscles.

nuchal line: Three lines that transversely cross the cranial rear. From lowest to highest they are:

inferior nuchal line extends across the middle of the nuchal lane, separating the nuchal muscles semispinalis capitis above from rectus capitis below.

superior nuchal line the most prominent, develops along the top of the semispinalis capitis muscle and some of the muscles lying over it attach directly to the line, trapezius more centrally and sternocleidomastoid more laterally. It separates the nuchal from the occipital planes of the occiput.

supreme nuchal line lies above the superior line, on the occipital plane. It may be totally absent, a distinct line dipping downward at the midline, or the superior border of the nuchal torus (if there is one).

nuchal plane (lower scale): The area at the nape of the neck where the neck muscles attach, the lower portion of the occipital bone below the superior nuchal line.

nuchal torus: A thickened bony prominence extending transversely across some or all of the back of the head, on the occipital bone, reflecting the pattern of muscle use as it separates the nuchal plane below from the occipital plane above.

nuclear family: A family unit consisting of parents and their dependent children.

nuclease: An enzyme that catalyzes the degradation of a nucleic acid by breaking phosphodiester bonds. Nucleases specific for DNA are termed deoxyribonucleases (DNases), and nucleases specific for RNA are termed ribonucleases (RNases).

nucleofilament: A fiber seen in chromatin. It is approximately 10 nm in diameter and consists of DNA wrapped around nucleosome cores.

nucleoid: Central region in a bacterial cell in which the chromosome is compacted.

nucleolus: An organelle within the eukaryotic nucleus; the site of transcription of the ribosomal RNA genes and assembly of the ribosomal subunits.

nucleoside phosphate: See nucleotide.

nucleosome: The basic structural unit of eukaryotic nuclear chromosomes, consisting of two molecules each of the four core histones (H2A, H2B, H3, and H4, the histone octamer), a single molecule of the linker histone H1, and about 180 bp of DNA.

nucleotide: A monomeric molecule of RNA and DNA that consists of three distinct parts: a pentose (ribose in RNA, deoxyribose in DNA), a nitrogenous base, and a phosphate group.

nucleus: A discrete structure within the cell that is bounded by a nuclear membrane. It contains most of the genetic material of the cell.

nullisomy: The aberrant, aneuploid state in a normally diploid cell or organism in which there is a loss of one pair of homologous chromosomes.

numerical dating: Age estimation in calendrical years before the present, also known as absolute dating, chronometric dating.